1. Field of the Invention
The present general inventive concept relates to an image display device with a sequential driving method, and more particularly, to an image display method to improve brightness of an output image of an image display device using a sequential driving method and a plurality of single-color light sources.
2. Description of the Related Art
Color display devices, such as plasma display panels (PDPs) and micro display (MD) devices, such as liquid crystal display (LCD) devices, liquid crystal on silicon (LCoS) devices, and digital micro mirror devices (DMDs), are widely used for computer monitors and TV sets.
In the display devices, a color image is realized by sequentially driving primary color image signals (red, green, and blue image signals) obtained from an original image signal at such a high speed to be undetectable to humans. A projection system uses a high intensity arc lamp as a light source and filters all colors except red, green, and blue from a light beam generated by the light source. Since an optical transport system for simultaneously displaying three primary color images requires three light sources and three optical paths, the optical transport system is heavy and large.
The weight of the optical transport system can be reduced by sequentially driving the three primary color image signals using a color wheel or a color filter with a single light source and by using a light path in common.
As illustrated in FIG. 1, the display devices generate RGB optical signals by sequentially filtering colors from an optical signal generated by one light source using a color wheel to realize lightweight devices, and use a conventional sequential driving method to sequentially drive the RGB optical signals.
However, according to a characteristic of the conventional sequential driving method, since an optical signal generated by one light source is divided into at least 3 signals, brightness of images output from the display devices is lowered. That is, the intensity of the images is only a third of the total light intensity due to the reflectivity of the color wheel or ribs of the color wheel. Accordingly, the display devices use a high power lamp or a high power electrode to have higher output optical intensity than a cathode ray tube.
To avoid large amounts of power consumption and heat generation problems due to the use of the high power lamp or the high power electrode, 4-color display devices enhancing brightness of output images by adding a white color component to 3 primary color components, as shown in FIG. 2, have been developed. The white color component can be obtained by projecting or reflecting the optical signal generated by the light source through or from a white color filter.
A conventional method of enhancing brightness of output images by adding a white color filter is disclosed in U.S. Pat. No. 5,233,385 in the name of Texas Instrument Incorporated entitled “White Light Enhanced Color Field Sequential Projection.”
A conventional device using the conventional method disclosed in U.S. Pat. No. 5,233,385 includes a white color filter in addition to 3 color filters, such as red (R), green (G), and blue (B) filters, and the brightness of output images can be enhanced in proportion to a size of the white color filter.
However, this conventional method of enhancing brightness deteriorates color saturation of pixels of an output image while enhancing the brightness of the output image since the white color filter enhances the brightness of a white color component, i.e., a non-chromatic component.
Another conventional method of enhancing brightness of an output image is disclosed in U.S. Pat. No. 5,929,843 in the name of Cannon Kabushiki Kaisha entitled “Image Processing Apparatus Which Extracts White Component Data.”
In this conventional method, 4 dots, such as red (R), green (G), blue (B), and white (W) dots, are used as a unit for representing a pixel in an LCD device, as shown in FIG. 3. Here, RGB data is transferred into the RGB dots, a white color component is extracted from the RGB data, and the white color component is transferred into the white dots. In this conventional method, the white color component is generated by non-linearly converting least common red, green, and blue data.
In this conventional method, white color complementing using the color wheel is performed in pixel units, and the size of the white color component can be determined according to an image signal. However, maintenance of color saturation to avoid a monochromatic tendency due to the addition of the white color component has not been considered. Therefore, when the brightness of an output image is increased, the color saturation is not maintained.
Recently, a conventional image display device for sequentially driving optical signals using LEDs, which are single-color light sources, has been developed. For example, a projection display system using LED light sources is disclosed in Korea Patent Publication No. 2002-82850. Here, a single-color light source, such as an LED or a laser diode, generates an optical signal having a shorter wavelength band than an optical signal generated by a white color light source, and singular in number. When an LCD is used as a display element, 3 RGB LEDs are sequentially driven, and a separate color filter is unnecessary for the LCD. In a conventional sequential driving method using this conventional image display device, driving of the single-color light sources is temporally limited, and a bright screen cannot be obtained due to the temporal limitation.